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 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
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package java.awt;

import java.awt.geom.AffineTransform;
import java.awt.geom.Point2D;
import java.awt.geom.Rectangle2D;
import java.awt.image.ColorModel;
import java.beans.ConstructorProperties;

/**
 * The {@code RadialGradientPaint} class provides a way to fill a shape with
 * a circular radial color gradient pattern. The user may specify 2 or more
 * gradient colors, and this paint will provide an interpolation between
 * each color.
 * <p>
 * The user must specify the circle controlling the gradient pattern,
 * which is described by a center point and a radius.  The user can also
 * specify a separate focus point within that circle, which controls the
 * location of the first color of the gradient.  By default the focus is
 * set to be the center of the circle.
 * <p>
 * This paint will map the first color of the gradient to the focus point,
 * and the last color to the perimeter of the circle, interpolating
 * smoothly for any in-between colors specified by the user.  Any line drawn
 * from the focus point to the circumference will thus span all the gradient
 * colors.
 * <p>
 * Specifying a focus point outside of the radius of the circle will cause
 * the rings of the gradient pattern to be centered on the point just inside
 * the edge of the circle in the direction of the focus point.
 * The rendering will internally use this modified location as if it were
 * the specified focus point.
 * <p>
 * The user must provide an array of floats specifying how to distribute the
 * colors along the gradient.  These values should range from 0.0 to 1.0 and
 * act like keyframes along the gradient (they mark where the gradient should
 * be exactly a particular color).
 * <p>
 * In the event that the user does not set the first keyframe value equal
 * to 0 and/or the last keyframe value equal to 1, keyframes will be created
 * at these positions and the first and last colors will be replicated there.
 * So, if a user specifies the following arrays to construct a gradient:<br>
 * <pre>
 *     {Color.BLUE, Color.RED}, {.3f, .7f}
 * </pre>
 * this will be converted to a gradient with the following keyframes:<br>
 * <pre>
 *     {Color.BLUE, Color.BLUE, Color.RED, Color.RED}, {0f, .3f, .7f, 1f}
 * </pre>
 *
 * <p>
 * The user may also select what action the {@code RadialGradientPaint} object
 * takes when it is filling the space outside the circle's radius by
 * setting {@code CycleMethod} to either {@code REFLECTION} or {@code REPEAT}.
 * The gradient color proportions are equal for any particular line drawn
 * from the focus point. The following figure shows that the distance AB
 * is equal to the distance BC, and the distance AD is equal to the distance DE.
 * <center>
 * <img src = "doc-files/RadialGradientPaint-3.png" alt="image showing the
 * distance AB=BC, and AD=DE">
 * </center>
 * If the gradient and graphics rendering transforms are uniformly scaled and
 * the user sets the focus so that it coincides with the center of the circle,
 * the gradient color proportions are equal for any line drawn from the center.
 * The following figure shows the distances AB, BC, AD, and DE. They are all equal.
 * <center>
 * <img src = "doc-files/RadialGradientPaint-4.png" alt="image showing the
 * distance of AB, BC, AD, and DE are all equal">
 * </center>
 * Note that some minor variations in distances may occur due to sampling at
 * the granularity of a pixel.
 * If no cycle method is specified, {@code NO_CYCLE} will be chosen by
 * default, which means the the last keyframe color will be used to fill the
 * remaining area.
 * <p>
 * The colorSpace parameter allows the user to specify in which colorspace
 * the interpolation should be performed, default sRGB or linearized RGB.
 *
 * <p>
 * The following code demonstrates typical usage of
 * {@code RadialGradientPaint}, where the center and focus points are
 * the same:
 * <pre>
 *     Point2D center = new Point2D.Float(50, 50);
 *     float radius = 25;
 *     float[] dist = {0.0f, 0.2f, 1.0f};
 *     Color[] colors = {Color.RED, Color.WHITE, Color.BLUE};
 *     RadialGradientPaint p =
 *         new RadialGradientPaint(center, radius, dist, colors);
 * </pre>
 *
 * <p>
 * This image demonstrates the example code above, with default
 * (centered) focus for each of the three cycle methods:
 * <center>
 * <img src = "doc-files/RadialGradientPaint-1.png" alt="image showing the
 * output of the sameple code">
 * </center>
 *
 * <p>
 * It is also possible to specify a non-centered focus point, as
 * in the following code:
 * <pre>
 *     Point2D center = new Point2D.Float(50, 50);
 *     float radius = 25;
 *     Point2D focus = new Point2D.Float(40, 40);
 *     float[] dist = {0.0f, 0.2f, 1.0f};
 *     Color[] colors = {Color.RED, Color.WHITE, Color.BLUE};
 *     RadialGradientPaint p =
 *         new RadialGradientPaint(center, radius, focus,
 *                                 dist, colors,
 *                                 CycleMethod.NO_CYCLE);
 * </pre>
 *
 * <p>
 * This image demonstrates the previous example code, with non-centered
 * focus for each of the three cycle methods:
 * <center>
 * <img src = "doc-files/RadialGradientPaint-2.png" alt="image showing the
 * output of the sample code">
 * </center>
 *
 * @author Nicholas Talian, Vincent Hardy, Jim Graham, Jerry Evans
 * @see java.awt.Paint
 * @see java.awt.Graphics2D#setPaint
 * @since 1.6
 */
public final class RadialGradientPaint extends MultipleGradientPaint {

  /**
   * Focus point which defines the 0% gradient stop X coordinate.
   */
  private final Point2D focus;

  /**
   * Center of the circle defining the 100% gradient stop X coordinate.
   */
  private final Point2D center;

  /**
   * Radius of the outermost circle defining the 100% gradient stop.
   */
  private final float radius;

  /**
   * Constructs a {@code RadialGradientPaint} with a default
   * {@code NO_CYCLE} repeating method and {@code SRGB} color space,
   * using the center as the focus point.
   *
   * @param cx the X coordinate in user space of the center point of the circle defining the
   * gradient.  The last color of the gradient is mapped to the perimeter of this circle.
   * @param cy the Y coordinate in user space of the center point of the circle defining the
   * gradient.  The last color of the gradient is mapped to the perimeter of this circle.
   * @param radius the radius of the circle defining the extents of the color gradient
   * @param fractions numbers ranging from 0.0 to 1.0 specifying the distribution of colors along
   * the gradient
   * @param colors array of colors to use in the gradient.  The first color is used at the focus
   * point, the last color around the perimeter of the circle.
   * @throws NullPointerException if {@code fractions} array is null, or {@code colors} array is
   * null
   * @throws IllegalArgumentException if {@code radius} is non-positive, or {@code fractions.length
   * != colors.length}, or {@code colors} is less than 2 in size, or a {@code fractions} value is
   * less than 0.0 or greater than 1.0, or the {@code fractions} are not provided in strictly
   * increasing order
   */
  public RadialGradientPaint(float cx, float cy, float radius,
      float[] fractions, Color[] colors) {
    this(cx, cy,
        radius,
        cx, cy,
        fractions,
        colors,
        CycleMethod.NO_CYCLE);
  }

  /**
   * Constructs a {@code RadialGradientPaint} with a default
   * {@code NO_CYCLE} repeating method and {@code SRGB} color space,
   * using the center as the focus point.
   *
   * @param center the center point, in user space, of the circle defining the gradient
   * @param radius the radius of the circle defining the extents of the color gradient
   * @param fractions numbers ranging from 0.0 to 1.0 specifying the distribution of colors along
   * the gradient
   * @param colors array of colors to use in the gradient.  The first color is used at the focus
   * point, the last color around the perimeter of the circle.
   * @throws NullPointerException if {@code center} point is null, or {@code fractions} array is
   * null, or {@code colors} array is null
   * @throws IllegalArgumentException if {@code radius} is non-positive, or {@code fractions.length
   * != colors.length}, or {@code colors} is less than 2 in size, or a {@code fractions} value is
   * less than 0.0 or greater than 1.0, or the {@code fractions} are not provided in strictly
   * increasing order
   */
  public RadialGradientPaint(Point2D center, float radius,
      float[] fractions, Color[] colors) {
    this(center,
        radius,
        center,
        fractions,
        colors,
        CycleMethod.NO_CYCLE);
  }

  /**
   * Constructs a {@code RadialGradientPaint} with a default
   * {@code SRGB} color space, using the center as the focus point.
   *
   * @param cx the X coordinate in user space of the center point of the circle defining the
   * gradient.  The last color of the gradient is mapped to the perimeter of this circle.
   * @param cy the Y coordinate in user space of the center point of the circle defining the
   * gradient.  The last color of the gradient is mapped to the perimeter of this circle.
   * @param radius the radius of the circle defining the extents of the color gradient
   * @param fractions numbers ranging from 0.0 to 1.0 specifying the distribution of colors along
   * the gradient
   * @param colors array of colors to use in the gradient.  The first color is used at the focus
   * point, the last color around the perimeter of the circle.
   * @param cycleMethod either {@code NO_CYCLE}, {@code REFLECT}, or {@code REPEAT}
   * @throws NullPointerException if {@code fractions} array is null, or {@code colors} array is
   * null, or {@code cycleMethod} is null
   * @throws IllegalArgumentException if {@code radius} is non-positive, or {@code fractions.length
   * != colors.length}, or {@code colors} is less than 2 in size, or a {@code fractions} value is
   * less than 0.0 or greater than 1.0, or the {@code fractions} are not provided in strictly
   * increasing order
   */
  public RadialGradientPaint(float cx, float cy, float radius,
      float[] fractions, Color[] colors,
      CycleMethod cycleMethod) {
    this(cx, cy,
        radius,
        cx, cy,
        fractions,
        colors,
        cycleMethod);
  }

  /**
   * Constructs a {@code RadialGradientPaint} with a default
   * {@code SRGB} color space, using the center as the focus point.
   *
   * @param center the center point, in user space, of the circle defining the gradient
   * @param radius the radius of the circle defining the extents of the color gradient
   * @param fractions numbers ranging from 0.0 to 1.0 specifying the distribution of colors along
   * the gradient
   * @param colors array of colors to use in the gradient.  The first color is used at the focus
   * point, the last color around the perimeter of the circle.
   * @param cycleMethod either {@code NO_CYCLE}, {@code REFLECT}, or {@code REPEAT}
   * @throws NullPointerException if {@code center} point is null, or {@code fractions} array is
   * null, or {@code colors} array is null, or {@code cycleMethod} is null
   * @throws IllegalArgumentException if {@code radius} is non-positive, or {@code fractions.length
   * != colors.length}, or {@code colors} is less than 2 in size, or a {@code fractions} value is
   * less than 0.0 or greater than 1.0, or the {@code fractions} are not provided in strictly
   * increasing order
   */
  public RadialGradientPaint(Point2D center, float radius,
      float[] fractions, Color[] colors,
      CycleMethod cycleMethod) {
    this(center,
        radius,
        center,
        fractions,
        colors,
        cycleMethod);
  }

  /**
   * Constructs a {@code RadialGradientPaint} with a default
   * {@code SRGB} color space.
   *
   * @param cx the X coordinate in user space of the center point of the circle defining the
   * gradient.  The last color of the gradient is mapped to the perimeter of this circle.
   * @param cy the Y coordinate in user space of the center point of the circle defining the
   * gradient.  The last color of the gradient is mapped to the perimeter of this circle.
   * @param radius the radius of the circle defining the extents of the color gradient
   * @param fx the X coordinate of the point in user space to which the first color is mapped
   * @param fy the Y coordinate of the point in user space to which the first color is mapped
   * @param fractions numbers ranging from 0.0 to 1.0 specifying the distribution of colors along
   * the gradient
   * @param colors array of colors to use in the gradient.  The first color is used at the focus
   * point, the last color around the perimeter of the circle.
   * @param cycleMethod either {@code NO_CYCLE}, {@code REFLECT}, or {@code REPEAT}
   * @throws NullPointerException if {@code fractions} array is null, or {@code colors} array is
   * null, or {@code cycleMethod} is null
   * @throws IllegalArgumentException if {@code radius} is non-positive, or {@code fractions.length
   * != colors.length}, or {@code colors} is less than 2 in size, or a {@code fractions} value is
   * less than 0.0 or greater than 1.0, or the {@code fractions} are not provided in strictly
   * increasing order
   */
  public RadialGradientPaint(float cx, float cy, float radius,
      float fx, float fy,
      float[] fractions, Color[] colors,
      CycleMethod cycleMethod) {
    this(new Point2D.Float(cx, cy),
        radius,
        new Point2D.Float(fx, fy),
        fractions,
        colors,
        cycleMethod);
  }

  /**
   * Constructs a {@code RadialGradientPaint} with a default
   * {@code SRGB} color space.
   *
   * @param center the center point, in user space, of the circle defining the gradient.  The last
   * color of the gradient is mapped to the perimeter of this circle.
   * @param radius the radius of the circle defining the extents of the color gradient
   * @param focus the point in user space to which the first color is mapped
   * @param fractions numbers ranging from 0.0 to 1.0 specifying the distribution of colors along
   * the gradient
   * @param colors array of colors to use in the gradient. The first color is used at the focus
   * point, the last color around the perimeter of the circle.
   * @param cycleMethod either {@code NO_CYCLE}, {@code REFLECT}, or {@code REPEAT}
   * @throws NullPointerException if one of the points is null, or {@code fractions} array is null,
   * or {@code colors} array is null, or {@code cycleMethod} is null
   * @throws IllegalArgumentException if {@code radius} is non-positive, or {@code fractions.length
   * != colors.length}, or {@code colors} is less than 2 in size, or a {@code fractions} value is
   * less than 0.0 or greater than 1.0, or the {@code fractions} are not provided in strictly
   * increasing order
   */
  public RadialGradientPaint(Point2D center, float radius,
      Point2D focus,
      float[] fractions, Color[] colors,
      CycleMethod cycleMethod) {
    this(center,
        radius,
        focus,
        fractions,
        colors,
        cycleMethod,
        ColorSpaceType.SRGB,
        new AffineTransform());
  }

  /**
   * Constructs a {@code RadialGradientPaint}.
   *
   * @param center the center point in user space of the circle defining the gradient.  The last
   * color of the gradient is mapped to the perimeter of this circle.
   * @param radius the radius of the circle defining the extents of the color gradient
   * @param focus the point in user space to which the first color is mapped
   * @param fractions numbers ranging from 0.0 to 1.0 specifying the distribution of colors along
   * the gradient
   * @param colors array of colors to use in the gradient.  The first color is used at the focus
   * point, the last color around the perimeter of the circle.
   * @param cycleMethod either {@code NO_CYCLE}, {@code REFLECT}, or {@code REPEAT}
   * @param colorSpace which color space to use for interpolation, either {@code SRGB} or {@code
   * LINEAR_RGB}
   * @param gradientTransform transform to apply to the gradient
   * @throws NullPointerException if one of the points is null, or {@code fractions} array is null,
   * or {@code colors} array is null, or {@code cycleMethod} is null, or {@code colorSpace} is null,
   * or {@code gradientTransform} is null
   * @throws IllegalArgumentException if {@code radius} is non-positive, or {@code fractions.length
   * != colors.length}, or {@code colors} is less than 2 in size, or a {@code fractions} value is
   * less than 0.0 or greater than 1.0, or the {@code fractions} are not provided in strictly
   * increasing order
   */
  @ConstructorProperties({"centerPoint", "radius", "focusPoint", "fractions", "colors",
      "cycleMethod", "colorSpace", "transform"})
  public RadialGradientPaint(Point2D center,
      float radius,
      Point2D focus,
      float[] fractions, Color[] colors,
      CycleMethod cycleMethod,
      ColorSpaceType colorSpace,
      AffineTransform gradientTransform) {
    super(fractions, colors, cycleMethod, colorSpace, gradientTransform);

    // check input arguments
    if (center == null) {
      throw new NullPointerException("Center point must be non-null");
    }

    if (focus == null) {
      throw new NullPointerException("Focus point must be non-null");
    }

    if (radius <= 0) {
      throw new IllegalArgumentException("Radius must be greater " +
          "than zero");
    }

    // copy parameters
    this.center = new Point2D.Double(center.getX(), center.getY());
    this.focus = new Point2D.Double(focus.getX(), focus.getY());
    this.radius = radius;
  }

  /**
   * Constructs a {@code RadialGradientPaint} with a default
   * {@code SRGB} color space.
   * The gradient circle of the {@code RadialGradientPaint} is defined
   * by the given bounding box.
   * <p>
   * This constructor is a more convenient way to express the
   * following (equivalent) code:<br>
   *
   * <pre>
   *     double gw = gradientBounds.getWidth();
   *     double gh = gradientBounds.getHeight();
   *     double cx = gradientBounds.getCenterX();
   *     double cy = gradientBounds.getCenterY();
   *     Point2D center = new Point2D.Double(cx, cy);
   *
   *     AffineTransform gradientTransform = new AffineTransform();
   *     gradientTransform.translate(cx, cy);
   *     gradientTransform.scale(gw / 2, gh / 2);
   *     gradientTransform.translate(-cx, -cy);
   *
   *     RadialGradientPaint gp =
   *         new RadialGradientPaint(center, 1.0f, center,
   *                                 fractions, colors,
   *                                 cycleMethod,
   *                                 ColorSpaceType.SRGB,
   *                                 gradientTransform);
   * </pre>
   *
   * @param gradientBounds the bounding box, in user space, of the circle defining the outermost
   * extent of the gradient
   * @param fractions numbers ranging from 0.0 to 1.0 specifying the distribution of colors along
   * the gradient
   * @param colors array of colors to use in the gradient.  The first color is used at the focus
   * point, the last color around the perimeter of the circle.
   * @param cycleMethod either {@code NO_CYCLE}, {@code REFLECT}, or {@code REPEAT}
   * @throws NullPointerException if {@code gradientBounds} is null, or {@code fractions} array is
   * null, or {@code colors} array is null, or {@code cycleMethod} is null
   * @throws IllegalArgumentException if {@code gradientBounds} is empty, or {@code fractions.length
   * != colors.length}, or {@code colors} is less than 2 in size, or a {@code fractions} value is
   * less than 0.0 or greater than 1.0, or the {@code fractions} are not provided in strictly
   * increasing order
   */
  public RadialGradientPaint(Rectangle2D gradientBounds,
      float[] fractions, Color[] colors,
      CycleMethod cycleMethod) {
    // gradient center/focal point is the center of the bounding box,
    // radius is set to 1.0, and then we set a scale transform
    // to achieve an elliptical gradient defined by the bounding box
    this(new Point2D.Double(gradientBounds.getCenterX(),
            gradientBounds.getCenterY()),
        1.0f,
        new Point2D.Double(gradientBounds.getCenterX(),
            gradientBounds.getCenterY()),
        fractions,
        colors,
        cycleMethod,
        ColorSpaceType.SRGB,
        createGradientTransform(gradientBounds));

    if (gradientBounds.isEmpty()) {
      throw new IllegalArgumentException("Gradient bounds must be " +
          "non-empty");
    }
  }

  private static AffineTransform createGradientTransform(Rectangle2D r) {
    double cx = r.getCenterX();
    double cy = r.getCenterY();
    AffineTransform xform = AffineTransform.getTranslateInstance(cx, cy);
    xform.scale(r.getWidth() / 2, r.getHeight() / 2);
    xform.translate(-cx, -cy);
    return xform;
  }

  /**
   * Creates and returns a {@link PaintContext} used to
   * generate a circular radial color gradient pattern.
   * See the description of the {@link Paint#createContext createContext} method
   * for information on null parameter handling.
   *
   * @param cm the preferred {@link ColorModel} which represents the most convenient format for the
   * caller to receive the pixel data, or {@code null} if there is no preference.
   * @param deviceBounds the device space bounding box of the graphics primitive being rendered.
   * @param userBounds the user space bounding box of the graphics primitive being rendered.
   * @param transform the {@link AffineTransform} from user space into device space.
   * @param hints the set of hints that the context object can use to choose between rendering
   * alternatives.
   * @return the {@code PaintContext} for generating color patterns.
   * @see Paint
   * @see PaintContext
   * @see ColorModel
   * @see Rectangle
   * @see Rectangle2D
   * @see AffineTransform
   * @see RenderingHints
   */
  public PaintContext createContext(ColorModel cm,
      Rectangle deviceBounds,
      Rectangle2D userBounds,
      AffineTransform transform,
      RenderingHints hints) {
    // avoid modifying the user's transform...
    transform = new AffineTransform(transform);
    // incorporate the gradient transform
    transform.concatenate(gradientTransform);

    return new RadialGradientPaintContext(this, cm,
        deviceBounds, userBounds,
        transform, hints,
        (float) center.getX(),
        (float) center.getY(),
        radius,
        (float) focus.getX(),
        (float) focus.getY(),
        fractions, colors,
        cycleMethod, colorSpace);
  }

  /**
   * Returns a copy of the center point of the radial gradient.
   *
   * @return a {@code Point2D} object that is a copy of the center point
   */
  public Point2D getCenterPoint() {
    return new Point2D.Double(center.getX(), center.getY());
  }

  /**
   * Returns a copy of the focus point of the radial gradient.
   * Note that if the focus point specified when the radial gradient
   * was constructed lies outside of the radius of the circle, this
   * method will still return the original focus point even though
   * the rendering may center the rings of color on a different
   * point that lies inside the radius.
   *
   * @return a {@code Point2D} object that is a copy of the focus point
   */
  public Point2D getFocusPoint() {
    return new Point2D.Double(focus.getX(), focus.getY());
  }

  /**
   * Returns the radius of the circle defining the radial gradient.
   *
   * @return the radius of the circle defining the radial gradient
   */
  public float getRadius() {
    return radius;
  }
}
